Sterling 30RA010-055 Thermistor Designations, Status Switches, Output Relays, Operating Data

At each system element, the shields of its communication bus cables must be tied together. If the communication bus is entirely within one building, the resulting continuous shield must be connected to a ground at one point only. If the commu- nication bus cable exits from one building and enters another, the shields must be connected to grounds at the lightning suppressor in each building where the cable enters or exits the building (one point per building only). To connect the unit to the network:

1.Turn off power to the control box.

2.Cut the SCN wire and strip the ends of the red (+), white (ground), and black (–) conductors. (Substitute appropri- ate colors for different colored cables.)

3.Connect the red wire to (+) terminal on TB3 of the plug, the white wire to COM terminal, and the black wire to the

(–) terminal.

4.The RJ14 SCN connector on TB3 can also be used, but is only intended for temporary connection (for example, a laptop computer running Service Tool).

IMPORTANT: A shorted SCN bus cable will prevent some routines from running and may prevent the unit from start- ing. If abnormal conditions occur, unplug the connector. If conditions return to normal, check the SCN connector and cable. Run new cable if necessary. A short in one section of the bus can cause problems with all system elements on the bus.

Table 2 — Thermistor Designations

THERMISTOR		PIN
		CONNECTION	THERMISTOR INPUT
NO.
		POINT
T1		J8-13,14 (MBB)	Cooler Leaving Fluid
T2		J8-11,12 (MBB)	Cooler Entering Fluid
T7		J8-1,2 (MBB)	Circuit A Return Gas
			Temperature (Accessory)
T8		J8-3,4 (MBB)	Circuit B (032-055 only) Return
			Gas Temperature (Accessory)
T9		J8-7,8 (MBB)	Outdoor-Air Temperature
			Sensor
T10		J8-5,6 (MBB)	Accessory Remote Space
		TB5-5,6	Temperature Sensor or
			Dual LWT Sensor
	LEGEND
LWT — Leaving Water Temperature
MBB — Main Base Board

Table 3 — Status Switches

STATUS	PIN CONNECTION
SWITCH	POINT
Chilled Water Pump 1	J7-1,2
Chilled Water Pump 2	J7-3,4
Remote On/Off	TB5-9,10
Cooler Flow Switch	J7-9,10
Compressor Fault Signal, A1	J9-11,12
Compressor Fault Signal, A2	J9-5,6
Compressor Fault Signal, B1	J9-8,9
Compressor Fault Signal, B2	J9-2,3

Table 4 — Output Relays

RELAY	DESCRIPTION
NO.
K1	Energize Compressor A1 (010-030)
	Energize Compressor A1 and Condenser Fan A1 (032-055)
K2	Energize Compressor B1 and Condenser Fan B1 at Low
	Speed (032-040)
	Energize Compressor B1 and Condenser Fan B1 (042-055)
K3	Energize Chilled Water Pump 1 Output
K4	Energize Chilled Water Pump 2 Output
K5	Energize Compressor A2 (all but 010, 015 60Hz)
K6	Energize Compressor B2 (042-055 only)
K7	Alarm Relay
K8	Cooler/Pump Heater
K9	Energize Condenser Fan at Low Speed (010-018)
	Energize Condenser Fan A1 (022-030)
	Energize Condenser Fan A2 (032-055)
	Energize Condenser Fan at High Speed (010-018)
K10	Energize Condenser Fan A2 (022-030)
	Energize Condenser Fan B1 at High Speed (032-040)
	Energize Condenser Fan B2 (042-055)
K11	Minimum Load Valve

Table 5 — SCN Communication Bus Wiring

MANUFACTURER	PART NO.
	Regular Wiring	Plenum Wiring
Alpha	1895	—
American	A21451	A48301
Belden	8205	884421
Columbia	D6451	—
Manhattan	M13402	M64430
Quabik	6130	—

OPERATING DATA

Sensors — The electronic control uses 3 to 6 thermistors to sense temperatures for controlling chiller operation. See Table 2. These sensors are outlined below. Thermistors T1, T2, T9 and accessory suction gas temperatures (T7,T8) are 5 kΩ at 77 F (25 C) and are identical in temperature versus resistance and voltage drop performance. Thermistor T10 is 10 kΩ at 77 F (25 C) and has a different temperature vs. resistance and voltage drop performance. See Thermistors section for temperature-resistance-voltage drop characteristics.

T1 — COOLER LEAVING FLUID SENSOR — On 30RA010- 030 sizes, this thermistor is installed in a friction fit well at the bottom of the brazed-plate heat exchanger on the control box side. For 30RA032-055 sizes, this thermistor is installed in a well in the factory-installed leaving fluid piping coming from the bottom of the brazed-plate heat exchanger opposite the control box side.

T2 — COOLER ENTERING FLUID SENSOR —On 30RA010- 030 sizes, this thermistor is installed in a friction fit well at the top of the brazed-plate heat exchanger on the control box side. For 30RA032-055 sizes, this thermistor is installed in a well in the factory-installed entering fluid piping coming from the top of the brazed-plate heat exchanger opposite the control box side.

T7,T8 — COMPRESSOR RETURN GAS TEMPERA- TURE SENSOR (ACCESSORY) — A well for this sensor is factory installed in each circuit's suction line. If desired, a 5 kΩ thermistor (Sterling part number HH79NZ029) can be installed in this well and connected to the Main Base Board as shown in Table 2. Use the Scrolling Marquee display to con- figure the sensor (Configuration mode, sub-mode OPT1 — enable item RG.EN).

T9 — OUTDOOR-AIR TEMPERATURE SENSOR — This sensor is factory-installed on a bracket at the left side of compressor A1 on 30RA010-030 models. For models 30RA032-055, it is installed behind the panel below the control box center door.

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